Olivia tried pushing her nerves away with pure excitement. She rushed up to Sebastian, ready to leap inside him, when her manners and anxiety came back. Looking into the piercing blue eyes of the man before her, "Thank you, sir. I'll try my best, I haven't done something like this before."
The energy of the room had been gradually leaving with the guests, and Olivia wasn't sure she could be successful in her attempts to possess him. She had never before possessed a full person, never mind a man, and now the reservoir of energy that gave her conscious life was running thin. The whole situation wasn't very hopeful, but this was the most exhilarating moment of her dead life and Olivia was not willing to let it end.
Unable to look into his eyes while doing this, Olivia turned her back to him, and started by first stepping her right foot back into his. Despite his slim frame, there was much more room in his body than she was used to, especially compared to the fly she entered this event in. Her excitement was surging back and her time was running out, so with her next step Olivia threw her back into his torso, bringing her whole body along with it, ending with her arms. At first she was lost, hoping she could easily jump into complete control as quickly as she jumped into his body, but that wasn't happening. Completely driven by intuition and sense, there was nothing she could do but give it all a shot and hope everything was lined up correctly. Near the end of the process Olivia could feel his deep-rooted faiths, torments, cares, and she had to use almost all her strength to stray away from his mind and separately insert her own, to control only the physical aspects of this being, and allow him to experience this with her, but him as the passenger. All of Olivia's hopes and attention were focused on doing this right, what Sebastian must have been going through was not something that crossed her mind.
Birds and flies are much easier to control.